Code-division-multiplexing using orthogonal codes for fast electrical impedance tomography

Abstract

Electrical impedance tomography (EIT) is used to determine the spatial conductivity distribution of a measurement environment, what involves several applications in the area of process engineering or medical science. In common systems a measurement environment is usually stimulated by defined current patterns in a serial time-multiplexing manner. Higher measurement rates can be achieved with code-multiplexed (CDM) excitations for parallel measurements. In order to optimize channel separation and dynamic range, orthogonal Walsh-Hadamard codes have been implemented on a fast EIT system. The crosstalk between different channels has been analyzed for 9 parallel coded excitation signals. Furthermore reconstructed conductivity distributions have been compared to reconstruction results obtained from frequency-multiplexed (FDM) measurements (root mean square difference of 0.02%).

Fast Electrical Impedance Tomography Based on Code-Division-Multiplexing Using Orthogonal Codes

“…In addition to [12], this paper contains a more detailed description of the signal processing, additional measurement results, and conductivity reconstruction experiments. Furthermore, the influences of frequency-dependent measurement objects on different excitation procedures are discussed.…”